//反转一个单链表。 
//
// 示例: 
//
// 输入: 1->2->3->4->5->NULL
//输出: 5->4->3->2->1->NULL 
//
// 进阶: 
//你可以迭代或递归地反转链表。你能否用两种方法解决这道题？ 
// Related Topics 链表 
// 👍 1447 👎 0

package leetcode.editor.cn;
//Java：反转链表
public class ReverseLinkedList{
    public static void main(String[] args) {
        Solution solution = new ReverseLinkedList().new Solution();
        
    }
    public class ListNode {
      int val;
      ListNode next;
      ListNode(int x) { val = x; }
   }
    //leetcode submit region begin(Prohibit modification and deletion)
/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode reverseList(ListNode head) {
        //递归实现
        if(  head == null || head.next == null ){
            return head;
        }

        ListNode newHead = reverseList(head.next);

        head.next.next = head;
        head.next = null;

        return newHead;
    }
}
//leetcode submit region end(Prohibit modification and deletion)

}
